JavaScript Object Id

user_128816 0
Viewed 146005

Do JavaScript objects/variables have some sort of unique identifier? Like Ruby has object_id. I don't mean the DOM id attribute, but rather some sort of memory address of some kind.

unique-id javascript
5 Answers

No, objects don't have a built in identifier, though you can add one by modifying the object prototype. Here's an example of how you might do that:

(function() {
    var id = 0;

    function generateId() { return id++; };

    Object.prototype.id = function() {
        var newId = generateId();

        this.id = function() { return newId; };

        return newId;
    };
})();

That said, in general modifying the object prototype is considered very bad practice. I would instead recommend that you manually assign an id to objects as needed or use a touch function as others have suggested.

user_539260

Actually, you don't need to modify the object prototype. The following should work to 'obtain' unique ids for any object, efficiently enough.

var __next_objid=1;
function objectId(obj) {
    if (obj==null) return null;
    if (obj.__obj_id==null) obj.__obj_id=__next_objid++;
    return obj.__obj_id;
}
user_1964620 

const log = console.log;

function* generateId() {
  for(let i = 0; ; ++i) {
    yield i;
  }
}

const idGenerator = generateId();

const ObjectWithId = new Proxy(Object, {
  construct(target, args) {
    const instance = Reflect.construct(target, args);
    instance['id'] = idGenerator.next().value;
    return instance;
  }
})

const myObject = new ObjectWithId({
  name: '@@NativeObject'
});

log(myObject.id);

user_138296570
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